/*
    * Licensed to the Apache Software Foundation (ASF) under one or more
    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * The ASF licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
    * the License.  You may obtain a copy of the License at
    *
    *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.commons.vfs2.provider;
  
  import java.io.File;
  import java.lang.reflect.InvocationTargetException;
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.Map;
  import java.util.Objects;
  import java.util.concurrent.atomic.AtomicInteger;
  import java.util.concurrent.atomic.AtomicLong;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.commons.vfs2.CacheStrategy;
  import org.apache.commons.vfs2.Capability;
  import org.apache.commons.vfs2.FileListener;
  import org.apache.commons.vfs2.FileName;
  import org.apache.commons.vfs2.FileObject;
  import org.apache.commons.vfs2.FileSelector;
  import org.apache.commons.vfs2.FileSystem;
  import org.apache.commons.vfs2.FileSystemConfigBuilder;
  import org.apache.commons.vfs2.FileSystemException;
  import org.apache.commons.vfs2.FileSystemManager;
  import org.apache.commons.vfs2.FileSystemOptions;
  import org.apache.commons.vfs2.FilesCache;
  import org.apache.commons.vfs2.VfsLog;
  import org.apache.commons.vfs2.cache.OnCallRefreshFileObject;
  import org.apache.commons.vfs2.events.AbstractFileChangeEvent;
  import org.apache.commons.vfs2.events.ChangedEvent;
  import org.apache.commons.vfs2.events.CreateEvent;
  import org.apache.commons.vfs2.events.DeleteEvent;
  import org.apache.commons.vfs2.impl.DefaultFileSystemConfigBuilder;
  import org.apache.commons.vfs2.util.FileObjectUtils;
  import org.apache.commons.vfs2.util.Messages;
  
  /**
   * A partial {@link org.apache.commons.vfs2.FileSystem} implementation.
   */
  public abstract class AbstractFileSystem extends AbstractVfsComponent implements FileSystem {
  
      private static final FileListener[] EMPTY_FILE_LISTENER_ARRAY = {};
  
      private static final Log LOG = LogFactory.getLog(AbstractFileSystem.class);
  
      /**
       * The "root" of the file system. This is always "/" so it isn't always the "real" root.
       */
      private final FileName rootName;
  
      /**
       * The root URI of the file system. The base path specified as a file system option when the file system was
       * created.
       */
      private final String rootURI;
  
      private final Collection<Capability> capabilities = new HashSet<>();
  
      private final FileObject parentLayer;
  
      /**
       * Map from FileName to an ArrayList of listeners for that file.
       */
      private final Map<FileName, ArrayList<FileListener>> listenerMap = new HashMap<>();
  
      /**
       * FileSystemOptions used for configuration
       */
      private final FileSystemOptions fileSystemOptions;
  
      /**
       * How many fileObjects are handed out
       */
      private final AtomicLong useCount = new AtomicLong();
  
      private FileSystemKey cacheKey;
  
      /**
       * open streams counter for this file system
       */
      private final AtomicInteger openStreams = new AtomicInteger();
  
     /**
      * Only provided for Serializable subclasses.
      */
     AbstractFileSystem() {
         this(null, null, null);
     }
 
     /**
      * Constructs a new instance.
      *
      * @param rootName The root file name of this file system.
      * @param parentLayer The parent layer of this file system.
      * @param fileSystemOptions Options to build this file system.
      */
     protected AbstractFileSystem(final FileName rootName, final FileObject parentLayer, final FileSystemOptions fileSystemOptions) {
         this.parentLayer = parentLayer;
         this.rootName = rootName;
         this.fileSystemOptions = fileSystemOptions;
         final FileSystemConfigBuilder builder = DefaultFileSystemConfigBuilder.getInstance();
         String uri = builder.getRootURI(fileSystemOptions);
         if (uri == null) {
             uri = rootName != null ? rootName.getURI() : null;
         }
         this.rootURI = uri;
     }
 
     /**
      * Adds the capabilities of this file system.
      *
      * @param caps collections of Capabilities, can be immutable.
      */
     protected abstract void addCapabilities(Collection<Capability> caps);
 
     /**
      * Adds a junction to this file system.
      *
      * @param junctionPoint The junction point.
      * @param targetFile The target to add.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public void addJunction(final String junctionPoint, final FileObject targetFile) throws FileSystemException {
         throw new FileSystemException("vfs.provider/junctions-not-supported.error", rootName);
     }
 
     /**
      * Adds a listener on a file in this file system.
      *
      * @param file The FileObject to be monitored.
      * @param listener The FileListener
      */
     @Override
     public void addListener(final FileObject file, final FileListener listener) {
         synchronized (listenerMap) {
             final ArrayList<FileListener> listeners = listenerMap.computeIfAbsent(file.getName(), k -> new ArrayList<>());
             listeners.add(listener);
         }
     }
 
     /**
      * Closes this component.
      */
     @Override
     public void close() {
         closeCommunicationLink();
     }
 
     /**
      * Closes the underlying link used to access the files.
      */
     public void closeCommunicationLink() {
         synchronized (this) {
             doCloseCommunicationLink();
         }
     }
 
     /**
      * Creates a file object.
      * <p>
      * This method is called only if the requested file is not cached.
      * </p>
      *
      * @param name name referencing the new file.
      * @return new created FileObject.
      * @throws Exception might throw an Exception, which is then wrapped in FileSystemException.
      */
     protected abstract FileObject createFile(AbstractFileName name) throws Exception;
 
     /**
      * Decorates the given file object.
      *
      * @param file the file object.
      * @return the decorated file object.
      * @throws FileSystemException if a file system error occurs.
      */
     protected FileObject decorateFileObject(FileObject file) throws FileSystemException {
         if (getFileSystemManager().getCacheStrategy().equals(CacheStrategy.ON_CALL)) {
             file = new OnCallRefreshFileObject(file);
         }
 
         if (getFileSystemManager().getFileObjectDecoratorConst() != null) {
             try {
                 file = (FileObject) getFileSystemManager().getFileObjectDecoratorConst().newInstance(file);
             } catch (final InstantiationException | IllegalAccessException | InvocationTargetException e) {
                 throw new FileSystemException("vfs.impl/invalid-decorator.error",
                         getFileSystemManager().getFileObjectDecorator().getName(), e);
             }
         }
 
         return file;
     }
 
     /**
      * Closes the underlying link used to access the files.
      */
     protected void doCloseCommunicationLink() {
         // default is noop.
     }
 
     /**
      * Creates a temporary local copy of a file and its descendants.
      *
      * @param file the start of the tree.
      * @param selector selection what to do with children.
      * @return replicated root file.
      * @throws Exception any Exception is wrapped as FileSystemException.
      */
     protected File doReplicateFile(final FileObject file, final FileSelector selector) throws Exception {
         return getContext().getReplicator().replicateFile(file, selector);
     }
 
     void fileObjectDestroyed(final FileObject fileObject) {
         useCount.decrementAndGet();
     }
 
     void fileObjectHanded(final FileObject fileObject) {
         useCount.incrementAndGet();
     }
 
     /**
      * Fires an event.
      */
     private void fireEvent(final AbstractFileChangeEvent event) {
         FileListener[] fileListeners = null;
         final FileObject fileObject = event.getFileObject();
 
         synchronized (listenerMap) {
             final ArrayList<?> listeners = listenerMap.get(fileObject.getName());
             if (listeners != null) {
                 fileListeners = listeners.toArray(EMPTY_FILE_LISTENER_ARRAY);
             }
         }
 
         if (fileListeners != null) {
             for (final FileListener fileListener : fileListeners) {
                 try {
                     event.notify(fileListener);
                 } catch (final Exception e) {
                     final String message = Messages.getString("vfs.provider/notify-listener.warn", fileObject);
                     // getLogger().warn(message, e);
                     VfsLog.warn(getLogger(), LOG, message, e);
                 }
             }
         }
     }
 
     /**
      * Fires a file changed event.
      * <p>
      * This will only happen if you monitor the file using {@link org.apache.commons.vfs2.FileMonitor}.
      * </p>
      *
      * @param file The FileObject that changed.
      */
     public void fireFileChanged(final FileObject file) {
         fireEvent(new ChangedEvent(file));
     }
 
     /**
      * Fires a file create event.
      *
      * @param file The FileObject that was created.
      */
     public void fireFileCreated(final FileObject file) {
         fireEvent(new CreateEvent(file));
     }
 
     /**
      * Fires a file delete event.
      *
      * @param file The FileObject that was deleted.
      */
     public void fireFileDeleted(final FileObject file) {
         fireEvent(new DeleteEvent(file));
     }
 
     void freeResources() {
         // default is noop.
     }
 
     /**
      * Gets the attribute with the specified name. The default implementation simply throws an exception.
      *
      * @param attrName The name of the attribute.
      * @return the Object associated with the attribute or null if no object is.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public Object getAttribute(final String attrName) throws FileSystemException {
         throw new FileSystemException("vfs.provider/get-attribute-not-supported.error");
     }
 
     FileSystemKey getCacheKey() {
         return cacheKey;
     }
 
     /**
      * Gets a cached file.
      *
      * @param name name to search for.
      * @return file object or null if not found.
      */
     protected FileObject getFileFromCache(final FileName name) {
         return getFilesCache().getFile(this, name);
     }
 
     private FilesCache getFilesCache() {
         final FilesCache filesCache = getContext().getFileSystemManager().getFilesCache();
         return Objects.requireNonNull(filesCache, () -> Messages.getString("vfs.provider/files-cache-missing.error"));
     }
 
     /**
      * Gets the FileSystemManager used to instantiate this file system.
      *
      * @return the FileSystemManager.
      */
     @Override
     public FileSystemManager getFileSystemManager() {
         return getContext().getFileSystemManager();
     }
 
     /**
      * Gets the FileSystemOptions used to instantiate this file system.
      *
      * @return the FileSystemOptions.
      */
     @Override
     public FileSystemOptions getFileSystemOptions() {
         return fileSystemOptions;
     }
 
     /**
      * Gets the accuracy of the last modification time.
      *
      * @return milliseconds, 0 means perfectly accurate, {@code > 0} might be off by this value, for examnple, sftp is 1000 milliseconds.
      */
     @Override
     public double getLastModTimeAccuracy() {
         return 0;
     }
 
     /**
      * Gets the parent layer if this is a layered file system.
      *
      * @return The FileObject for the parent layer.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public FileObject getParentLayer() throws FileSystemException {
         return parentLayer;
     }
 
     /**
      * Gets the root file of this file system.
      *
      * @return The root FileObject of the FileSystem
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public FileObject getRoot() throws FileSystemException {
         return resolveFile(rootName);
     }
 
     /**
      * Gets the name of the root of this file system.
      *
      * @return the root FileName.
      */
     @Override
     public FileName getRootName() {
         return rootName;
     }
 
     /**
      * Gets the root URI specified for this file System.
      *
      * @return The root URI used in this file system.
      * @since 2.0
      */
     @Override
     public String getRootURI() {
         return rootURI;
     }
 
     /**
      * Tests whether this file system has a particular capability.
      *
      * @param capability the Capability to check for.
      * @return true if the FileSystem has the Capability, false otherwise.
      */
     @Override
     public boolean hasCapability(final Capability capability) {
         return capabilities.contains(capability);
     }
 
     /**
      * Initializes this component.
      *
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public void init() throws FileSystemException {
         addCapabilities(capabilities);
     }
 
     /**
      * Tests whether this file system has open streams.
      *
      * @return true if the FileSystem has open streams.
      */
     public boolean isOpen() {
         return openStreams.get() > 0;
     }
 
     /**
      * Tests whether any files are using this FileSystem.
      *
      * @return whether any files are using this FileSystem.
      */
     public boolean isReleaseable() {
         return useCount.get() < 1;
     }
 
     /**
      * Called after all file-objects closed their streams.
      */
     protected void notifyAllStreamsClosed() {
         // default is noop.
     }
 
     /**
      * Adds a file object to the cache.
      *
      * @param file the file to add.
      */
     protected void putFileToCache(final FileObject file) {
         getFilesCache().putFile(file);
     }
 
     /**
      * Removes a cached file.
      *
      * @param name The file name to remove.
      */
     protected void removeFileFromCache(final FileName name) {
         getFilesCache().removeFile(this, name);
     }
 
     /**
      * Removes a junction from this file system.
      *
      * @param junctionPoint The junction point.
      * @throws FileSystemException if an error occurs
      */
     @Override
     public void removeJunction(final String junctionPoint) throws FileSystemException {
         throw new FileSystemException("vfs.provider/junctions-not-supported.error", rootName);
     }
 
     /**
      * Removes a listener from a file in this file system.
      *
      * @param file The FileObject to be monitored.
      * @param listener The FileListener
      */
     @Override
     public void removeListener(final FileObject file, final FileListener listener) {
         synchronized (listenerMap) {
             final ArrayList<?> listeners = listenerMap.get(file.getName());
             if (listeners != null) {
                 listeners.remove(listener);
                 if (listeners.isEmpty()) {
                     listenerMap.remove(file.getName());
                 }
             }
         }
     }
 
     /**
      * Creates a temporary local copy of a file and its descendants.
      *
      * @param file The FileObject to replicate.
      * @param selector The FileSelector.
      * @return The replicated File.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public File replicateFile(final FileObject file, final FileSelector selector) throws FileSystemException {
         if (!FileObjectUtils.exists(file)) {
             throw new FileSystemException("vfs.provider/replicate-missing-file.error", file.getName());
         }
 
         try {
             return doReplicateFile(file, selector);
         } catch (final Exception e) {
             throw new FileSystemException("vfs.provider/replicate-file.error", file.getName(), e);
         }
     }
 
     /**
      * Finds a file in this file system.
      *
      * @param name The name of the file to locate.
      * @return The located FileObject or null if none could be located.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public FileObject resolveFile(final FileName name) throws FileSystemException {
         return resolveFile(name, true);
     }
 
     private synchronized FileObject resolveFile(final FileName name, final boolean useCache)
             throws FileSystemException {
         if (!rootName.getRootURI().equals(name.getRootURI())) {
             throw new FileSystemException("vfs.provider/mismatched-fs-for-name.error", name, rootName,
                     name.getRootURI());
         }
 
         // imario@apache.org ==> use getFileFromCache
         FileObject file;
         if (useCache) {
             file = getFileFromCache(name);
         } else {
             file = null;
         }
 
         if (file == null) {
             try {
                 file = createFile((AbstractFileName) name);
             } catch (final Exception e) {
                 throw new FileSystemException("vfs.provider/resolve-file.error", name, e);
             }
 
             file = decorateFileObject(file);
 
             // imario@apache.org ==> use putFileToCache
             if (useCache) {
                 putFileToCache(file);
             }
         }
 
         /*
           resync the file information if requested
          */
         if (getFileSystemManager().getCacheStrategy().equals(CacheStrategy.ON_RESOLVE)) {
             file.refresh();
         }
         return file;
     }
 
     /**
      * Finds a file in this file system.
      *
      * @param nameStr The name of the file to resolve.
      * @return The located FileObject or null if none could be located.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public FileObject resolveFile(final String nameStr) throws FileSystemException {
         // Resolve the name, and create the file
         return resolveFile(getFileSystemManager().resolveName(rootName, nameStr));
     }
 
     /**
      * Sets the attribute with the specified name. The default implementation simply throws an exception.
      *
      * @param attrName the attribute name.
      * @param value The object to associate with the attribute.
      * @throws FileSystemException if an error occurs.
      */
     @Override
     public void setAttribute(final String attrName, final Object value) throws FileSystemException {
         throw new FileSystemException("vfs.provider/set-attribute-not-supported.error");
     }
 
     void setCacheKey(final FileSystemKey cacheKey) {
         this.cacheKey = cacheKey;
     }
 
     void streamClosed() {
         if (openStreams.decrementAndGet() == 0) {
             notifyAllStreamsClosed();
         }
     }
 
     void streamOpened() {
         openStreams.incrementAndGet();
     }
 }